/*
  ==============================================================================

   This file is part of the JUCE framework.
   Copyright (c) Raw Material Software Limited

   JUCE is an open source framework subject to commercial or open source
   licensing.

   By downloading, installing, or using the JUCE framework, or combining the
   JUCE framework with any other source code, object code, content or any other
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   the JUCE Website Terms of Service, as applicable, which will bind you. If you
   do not agree to the terms of these agreements, we will not license the JUCE
   framework to you, and you must discontinue the installation or download
   process and cease use of the JUCE framework.

   JUCE End User Licence Agreement: https://juce.com/legal/juce-8-licence/
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   JUCE Website Terms of Service: https://juce.com/juce-website-terms-of-service/

   Or:

   You may also use this code under the terms of the AGPLv3:
   https://www.gnu.org/licenses/agpl-3.0.en.html

   THE JUCE FRAMEWORK IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL
   WARRANTIES, WHETHER EXPRESSED OR IMPLIED, INCLUDING WARRANTY OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, ARE DISCLAIMED.

  ==============================================================================
*/

namespace juce::dsp
{

/**
    Generates a signal based on a user-supplied function.

    @tags{DSP}
*/
template <typename SampleType>
class Oscillator
{
public:
    /** The NumericType is the underlying primitive type used by the SampleType (which
        could be either a primitive or vector)
    */
    using NumericType = typename SampleTypeHelpers::ElementType<SampleType>::Type;

    /** Creates an uninitialised oscillator. Call initialise before first use. */
    Oscillator() = default;

    /** Creates an oscillator with a periodic input function (-pi..pi).

        If lookup table is not zero, then the function will be approximated
        with a lookup table.
    */
    Oscillator (const std::function<NumericType (NumericType)>& function,
                size_t lookupTableNumPoints = 0)
    {
        initialise (function, lookupTableNumPoints);
    }

    /** Returns true if the Oscillator has been initialised. */
    bool isInitialised() const noexcept     { return static_cast<bool> (generator); }

    /** Initialises the oscillator with a waveform. */
    void initialise (const std::function<NumericType (NumericType)>& function,
                     size_t lookupTableNumPoints = 0)
    {
        if (lookupTableNumPoints != 0)
        {
            auto* table = new LookupTableTransform<NumericType> (function,
                                                                 -MathConstants<NumericType>::pi,
                                                                 MathConstants<NumericType>::pi,
                                                                 lookupTableNumPoints);

            lookupTable.reset (table);
            generator = [table] (NumericType x) { return (*table) (x); };
        }
        else
        {
            generator = function;
        }
    }

    //==============================================================================
    /** Sets the frequency of the oscillator. */
    void setFrequency (NumericType newFrequency, bool force = false) noexcept
    {
        if (force)
        {
            frequency.setCurrentAndTargetValue (newFrequency);
            return;
        }

        frequency.setTargetValue (newFrequency);
    }

    /** Returns the current frequency of the oscillator. */
    NumericType getFrequency() const noexcept                    { return frequency.getTargetValue(); }

    //==============================================================================
    /** Called before processing starts. */
    void prepare (const ProcessSpec& spec) noexcept
    {
        sampleRate = static_cast<NumericType> (spec.sampleRate);
        rampBuffer.resize ((int) spec.maximumBlockSize);

        reset();
    }

    /** Resets the internal state of the oscillator */
    void reset() noexcept
    {
        phase.reset();

        if (sampleRate > 0)
            frequency.reset (sampleRate, 0.05);
    }

    //==============================================================================
    /** Returns the result of processing a single sample. */
    SampleType JUCE_VECTOR_CALLTYPE processSample (SampleType input) noexcept
    {
        jassert (isInitialised());
        auto increment = MathConstants<NumericType>::twoPi * frequency.getNextValue() / sampleRate;
        return input + generator (phase.advance (increment) - MathConstants<NumericType>::pi);
    }

    /** Processes the input and output buffers supplied in the processing context. */
    template <typename ProcessContext>
    void process (const ProcessContext& context) noexcept
    {
        jassert (isInitialised());
        auto&& outBlock = context.getOutputBlock();
        auto&& inBlock  = context.getInputBlock();

        // this is an output-only processor
        jassert (outBlock.getNumSamples() <= static_cast<size_t> (rampBuffer.size()));

        auto len           = outBlock.getNumSamples();
        auto numChannels   = outBlock.getNumChannels();
        auto inputChannels = inBlock.getNumChannels();
        auto baseIncrement = MathConstants<NumericType>::twoPi / sampleRate;

        if (context.isBypassed)
            context.getOutputBlock().clear();

        if (frequency.isSmoothing())
        {
            auto* buffer = rampBuffer.getRawDataPointer();

            for (size_t i = 0; i < len; ++i)
                buffer[i] = phase.advance (baseIncrement * frequency.getNextValue())
                              - MathConstants<NumericType>::pi;

            if (! context.isBypassed)
            {
                size_t ch;

                if (context.usesSeparateInputAndOutputBlocks())
                {
                    for (ch = 0; ch < jmin (numChannels, inputChannels); ++ch)
                    {
                        auto* dst = outBlock.getChannelPointer (ch);
                        auto* src = inBlock.getChannelPointer (ch);

                        for (size_t i = 0; i < len; ++i)
                            dst[i] = src[i] + generator (buffer[i]);
                    }
                }
                else
                {
                    for (ch = 0; ch < jmin (numChannels, inputChannels); ++ch)
                    {
                        auto* dst = outBlock.getChannelPointer (ch);

                        for (size_t i = 0; i < len; ++i)
                            dst[i] += generator (buffer[i]);
                    }
                }

                for (; ch < numChannels; ++ch)
                {
                    auto* dst = outBlock.getChannelPointer (ch);

                    for (size_t i = 0; i < len; ++i)
                        dst[i] = generator (buffer[i]);
                }
            }
        }
        else
        {
            auto freq = baseIncrement * frequency.getNextValue();
            auto p = phase;

            if (context.isBypassed)
            {
                frequency.skip (static_cast<int> (len));
                p.advance (freq * static_cast<NumericType> (len));
            }
            else
            {
                size_t ch;

                if (context.usesSeparateInputAndOutputBlocks())
                {
                    for (ch = 0; ch < jmin (numChannels, inputChannels); ++ch)
                    {
                        p = phase;
                        auto* dst = outBlock.getChannelPointer (ch);
                        auto* src = inBlock.getChannelPointer (ch);

                        for (size_t i = 0; i < len; ++i)
                            dst[i] = src[i] + generator (p.advance (freq) - MathConstants<NumericType>::pi);
                    }
                }
                else
                {
                    for (ch = 0; ch < jmin (numChannels, inputChannels); ++ch)
                    {
                        p = phase;
                        auto* dst = outBlock.getChannelPointer (ch);

                        for (size_t i = 0; i < len; ++i)
                            dst[i] += generator (p.advance (freq) - MathConstants<NumericType>::pi);
                    }
                }

                for (; ch < numChannels; ++ch)
                {
                    p = phase;
                    auto* dst = outBlock.getChannelPointer (ch);

                    for (size_t i = 0; i < len; ++i)
                        dst[i] = generator (p.advance (freq) - MathConstants<NumericType>::pi);
                }
            }

            phase = p;
        }
    }

private:
    //==============================================================================
    std::function<NumericType (NumericType)> generator;
    std::unique_ptr<LookupTableTransform<NumericType>> lookupTable;
    Array<NumericType> rampBuffer;
    SmoothedValue<NumericType> frequency { static_cast<NumericType> (440.0) };
    NumericType sampleRate = 48000.0;
    Phase<NumericType> phase;
};

} // namespace juce::dsp
